Binding contrib guide (#6864)

packages/wrangler/docs/how-to/add-a-binding.md

@@ -0,0 +1,18 @@
+# How to register a binding
+
+1. Register `wrangler.toml` section in: `packages/wrangler/src/config/environment.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/config/environment.ts#L431-L451)
+1. Register validation functions in: `packages/wrangler/src/config/validation.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/config/validation.ts#L1297-L1306)
+1. Add empty state for bindings, as necessary (tip: use typescript to guide you -- either via your editor or run: `pnpm check:type` from within `packages/wrangler`)
+1. Add type for deployment bundle to:
+   - `CfWorkerInit` in: `packages/wrangler/src/deployment-bundle/worker.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/deployment-bundle/worker.ts#L79C1-L85C2)
+   - `WorkerMetadataBinding` in: `packages/wrangler/src/deployment-bundle/create-worker-upload-form.ts` [ref-1](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/deployment-bundle/create-worker-upload-form.ts#L65) [ref-2](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/deployment-bundle/create-worker-upload-form.ts#L219-L225)
+1. Add type to DevEnv `Binding` union in: `packages/wrangler/src/api/startDevWorker/types.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/api/startDevWorker/types.ts#L246)
+1. Add user-friendly output for `printBindings` in: `packages/wrangler/src/config/index.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/config/index.ts#L270-L280)
+1. Add mapping functions to:
+   - `createWorkerUploadForm` in: `packages/wrangler/src/deployment-bundle/create-worker-upload-form.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/deployment-bundle/create-worker-upload-form.ts#L219-L225)
+   - `convertCfWorkerInitBindingstoBindings` in: `packages/wrangler/src/api/startDevWorker/utils.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/api/startDevWorker/utils.ts#L118-L123)
+   - `convertBindingsToCfWorkerInitBindings` in: `packages/wrangler/src/api/startDevWorker/utils.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/api/startDevWorker/utils.ts#L303-L305)
+1. Test binding is deployed and printed in: `packages/wrangler/src/**tests**/deploy.test.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/__tests__/deploy.test.ts#L7604)
+1. Test your validation in: `packages/wrangler/src/**tests**/configuration.test.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/__tests__/configuration.test.ts#L2234)
+1. Enable `wrangler init --from-dash` to include your binding in the `wrangler.toml` it generates in: `packages/wrangler/src/init.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/init.ts#L1036-L1043)
+1. Enable `wrangler types` to emit your binding type in: `packages/src/type-generation/index.ts` [ref](https://github.com/cloudflare/workers-sdk/blob/ce7db9d9cb4f5bcd5a326b86dde051cb54b999fb/packages/wrangler/src/type-generation/index.ts#L115)